Fixed wrong error message when importing RSA private key #1034

Job	Run time
mypy	13s
build_python_27 (ubuntu-22.04, yes)	42s
build_python_27 (ubuntu-22.04, no)	46s
build (3.7, yes, ubuntu-22.04)	2m 43s
python_no_gil	5m 32s
build_python_27 (windows-latest, yes)	36s
build (3.7, no, ubuntu-22.04)	2m 45s
test_c_linux (0, x64)	49s
build_python_27 (windows-latest, no)	39s
build (3.8, yes, ubuntu-22.04)	2m 36s
test_c_linux (0, x32)	1m 8s
build (3.8, no, ubuntu-22.04)	2m 26s
test_c_linux (1, x64)	48s
test_c_windows (x64)	35s
build (3.9, yes, ubuntu-22.04)	2m 55s
test_c_windows (win32)	48s
test_c_linux (1, x32)	1m 8s
build (3.9, no, ubuntu-22.04)	2m 54s
build (3.10, yes, ubuntu-22.04)	2m 55s
build (3.10, no, ubuntu-22.04)	2m 57s
build (3.11, yes, ubuntu-22.04)	2m 56s
build (3.11, no, ubuntu-22.04)	2m 56s
build (3.12, yes, ubuntu-22.04)	2m 54s
build (3.12, no, ubuntu-22.04)	2m 55s
build (3.13, yes, ubuntu-22.04)	2m 54s
build (3.13, no, ubuntu-22.04)	2m 55s
build (3.13, yes, macos-13)	2m 55s
build (3.13, no, windows-latest)	2m 50s
build (3.13, yes, windows-latest)	2m 48s
build (pypy2.7, no, ubuntu-latest)	33s
build (pypy3.9, no, ubuntu-latest)	18s
build (3.13, yes, ubuntu-22.04-arm)	2m 56s
	1h 5m 45s

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